CPU

Table of Contents Introduction SIMD Implementation Fundamentals 2.1 AVX2 and 256-bit Registers 2.2 Memory Alignment Considerations 2.2.1 Unaligned Memory Access (Inefficient) 2.2.2 Aligned Memory Access (Efficient) 2.3 Loop Unrolling Technique 2.4 Compilation Requirements SIMD in Practice: Dot Product Case Study 3.1 Four Implementation Approaches 3.1.1 Scalar Implementation (Baseline) 3.1.2 Basic SIMD Implementation 3.1.3 Unrolled SIMD Implementation 3.1.4 Aligned SIMD Implementation Performance Analysis: Benchmark Results 4.1 Compilation Methodology 4.2 Results with -O3 Optimization 4.3 Results without -O3 Optimization 4.4 Compiler Optimization vs Manual SIMD: Key Insights 4.4.1 Compiler Auto-Vectorization is Remarkably Effective 4.4.2 Manual Optimization Value Depends on Context 4.4.3 Memory Hierarchy Effects Persist Regardless Conclusion & Practical Takeaways 5.1 Key Practical Takeaways 1. Introduction Do you keep hearing SIMD but don’t know what it is all about? Here is an article for you. SIMD is the go-to technique for squeezing every ounce of performance from modern CPUs. The promise of SIMD is: process 8 floating-point numbers simultaneously instead of one and in theory that will achieve 8x speed. That is just theory because there are other parameters that impact the results. ...